The present invention relates to a display device having a pixel structure, that includes a liquid crystal display device (hereinafter, referred to as an LCD), a plasma display panel (hereinafter, referred to as a PDP), and the like. The display device is capable of making the existence of an electrically uncontrollable dot (hereinafter, referred to as a defective dot) more unnoticeable.
When manufacturing a display device, in which dots of three colors constituting minute pixels of an LCD, a PDP, and the like are spaciously arranged, a defective dot appears out of several millions dots. Such a defective dot cannot control intensity of light, so that a pixel including the dot cannot freely develop a color. Therefore, even in the event of a defect at an extremely small rate, e.g., one out of several million pixels, picture quality is seriously affected. For this reason, such a display device requires strict screening before delivery, resulting in a problem such as an increase in overall cost and an obstacle to wide use.
FIG. 7 is an explanatory drawing showing a model of display device having a defective dot. In FIG. 7, dots 201 represent red, dots 202 represent blue, dots 203 represent green, 204 represents a black matrix, and the colors are aligned in longitudinal stripes. In FIG. 7, hatched parts are illuminated parts. Namely, FIG. 7 shows an enlarged part of the surface entirely illuminated in blue on the display device. The following explanation is made on the assumption that only the blue dots 202 are entirely illuminated.
Assuming that a blue dot 205 is defective and is shown as a black dot, although the entire surface needs to be illuminated in blue, the defective dot cannot be illuminated. Consequently, irregular colors appear on the surface so as to cause deterioration in picture quality.
As for such a defective dot, the fundamental solution is to improve its manufacturing technique. For example, a method of improving the precision and cleaning a manufacturing apparatus is applicable.
Another method is applicable, in which a circuit pattern, etc. is modified for correcting a defective dot found in inspection after manufacturing. When a defective dot can undergo some processing after manufacturing, a method has been adopted in which the circuit is burned off and sintered using a laser device to make the defective dot more unnoticeable.
Conventionally, the foregoing two methods have been mainly adopted. To be specific, the manufacturing technology is improved, or a processing is performed after manufacturing, so that a reduction of a defective ratio is achieved, thereby reducing the overall cost.
However, the conventional methods require a large amount of cost. For example, when introducing equipment with high ability of cleaning, the cost is extremely large. Further, it is also costly to maintain the cleaning ability.
Moreover, regarding the method of making a defective dot unnoticeable by burning off or sintering a circuit with a laser device, etc., the following problems occur:
Firstly, the result of the method cannot be freely selected. To be specific, the laser device has only two alternatives of burning off or sintering the circuit, so that it is only possible to permanently make the defective dot non-conductive or bring it into conduction. Therefore, the defective dot is entirely illuminated (luminescent spot defect) or unilluminated (black spot defect). Only a few defects can be solved by the foregoing methods; hence, the foregoing technique by itself cannot dramatically reduce the overall defective ratio.
Next, the methods have an extremely small throughput, which means that long time is required to analyze the content of a defect, to judge which circuit and how it should be burned off or sintered, and to perform the operation. For this reason, the foregoing methods cannot efficiently reduce defects.
Considering the above two problems, even when the foregoing methods are used with the laser device, it is fairly impossible to dramatically reduce an overall defective ratio.
Consequently, either improvement of the manufacturing technique or the method using a laser device, etc. requires a large amount of cost, resulting in a problem such as an increase in the overall cost.
The objective of the present invention is to provide a display device which is can suppress a display defect caused by a defective dot, which is electrically uncontrollable, in a desirable manner, and which can decrease the cost for correcting a defect.
Another objective of the present invention is to provide a display device which can further simplify its circuit construction.
In order to attain the above objectives, the display of the present invention, in which dots of three colors constituting a fine pixel are spatially arranged, includes a means for controlling a signal applied to a dot adjacent to an electrically uncontrollable dot, in order to reduce visual deterioration caused by the electrically uncontrollable dot.
According to the above invention, even when a defective dot, which is electrically uncontrollable, occurs in the display device, it is possible to generate brightness substantially equal to original brightness of the defective dot, by controlling a signal applied to one or more dots adjacent to the defective dot. Consequently, it is possible to suppress visual deterioration (display defect) caused by the defective dot. Moreover, the present invention does not cause the foregoing problems that appear in the conventional method using a laser device.
Here, xe2x80x9cadjacent to . . . xe2x80x9d means that a dot is adjacent to the defective dot horizontally, vertically, or diagonally.
In order to attain the foregoing objectives, another display device of the present invention, which has a plurality of pixels, each pixel displaying by dots of at least three colors, includes a control means for controlling a signal applied to a plurality of dots adjacent to the defective dot so as to reduce a difference between a) a color obtained by illumination of the plurality of dots and b) an original color obtained by input signals to the defective dot and the plurality of dots, in order to compensate for a display defect caused by the defective dot which is electrically uncontrollable,
wherein the control means performs an operation based on a function, which is obtained by correlation relationship between an original input signal of the defective dot and a signal value to be applied to one of the plurality of dots in response to the input signal of the defective dot, so as to determine a signal value applied to the one of the plurality of dots, and then, the control means determines a signal value applied to another dot.
According to the present invention, signals applied to the plurality of dots are controlled such that a difference is reduced (preferably to a minimum) between a) a color obtained by illumination of the plurality of dots adjacent to a defective dot and b) an original color obtained by input signals to the defective dot and the plurality of dots. With this arrangement, a color around the defective dot is virtually equal to an original color of the defective dot, thereby suppressing a display defect caused by the defective dot. Further, the present invention does not cause the foregoing problems that appear in the conventional method using a laser device.
Furthermore, the control means performs an operation based on a function, which is obtained by a correlation relationship between an original input signal of the defective dot and a signal value to be applied to one of the plurality of dots in response to the input signal of the defective dot, so as to determine a signal value applied to the one of the plurality of dots. It is therefore possible to determine a signal value applied to the one of the dots by relatively simple operation, thereby simplifying the circuit construction.
The present invention is suitably adopted for a liquid crystal display device and so on. Additionally, the present invention is applicable to the other display devices such as a plasma display device and an electroluminescence display device. Moreover, the present invention is not limited to a display device for providing a color display with a single display panel but is also adopted for a projection display system (such as a liquid crystal projector) and the like, which is provided with a plurality of panels corresponding to colors and provides a color display by synthesizing light transmitted from the panels.